1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus and a method of controlling the same, which develops an electrostatic latent image formed on a photoconductive medium.
2. Description of the Related Art
Generally, an electrophotographic image forming apparatus such as a laser printer, a copier, or a facsimile machine obtains a desired image by adhering toner onto an electrostatic latent image formed on a photoconductive medium, developing the electrostatic latent image, and transferring the developed toner image to a printing paper.
FIG. 1 illustrates a general conventional image forming apparatus including a laser scanning unit (LSU) 10 which generates a laser beam, a photoconductive medium 20 on which an electrostatic latent image is formed by the generated laser beam and an electrifying apparatus 30 which electrifies a surface of the photoconductive medium 20 to a predetermined electric potential. The conventional image forming apparatus also includes a developing unit 40 which forms a toner image by adhering a toner onto an electrostatic latent image of the photoconductive medium 20, a transferring unit 50 which transfers the toner image formed on the photoconductive medium 20 to a paper P, a fusing unit 60 which fuses the transferred toner image on the paper P, and a paper supplying unit 70 which supplies the paper P.
The developing unit 40 includes four developing apparatuses 42, 43, 44, 45 supplying color toner of yellow, magenta, cyan and black, respectively. The developing apparatuses 42, 43, 44, 45 each include a toner receptacle 46 to store the color toner, a developing roller 47 to adhere the color toner stored in the toner receptacle 46 onto the electrostatic latent image of the photoconductive medium 20, and a gap ring 48 to maintain a predetermined gap between the developing roller 47 and the photoconductive medium 20. The developing apparatuses 42, 43, 44, 45 are disposed on a circular turret 41 at a predetermined interval, and are moved toward the photoconductive medium 20 by rotation of the turret 41.
The transferring unit 50 includes a transfer belt 51 to transfer the toner image formed on the photoconductive medium 20 to the paper P, a first transfer roller 52 to transfer the toner image to the transfer belt 51, and a second transfer roller 53 to transfer the toner image which is transferred to the transfer belt 51 to the paper P.
In the conventional image forming apparatus, when the LSU 10 scans a laser beam to the photoconductive medium 20 electrified by the electrifying apparatus 30, the electrostatic latent image is formed as the electric potential becomes low where the laser beam is scanned. If the yellow developing apparatus 42 approaches the photoconductive medium 20 as the turret 41 rotates, a gap is formed between the developing roller 47 and the photoconductive medium 20 by a contact of the gap ring 48 with a surface of the photoconductive medium 20. At this time, the yellow toner in the toner receptacle 46 is adhered onto the electrostatic latent image formed on the photoconductive medium 20 by the developing roller 47. The yellow toner image formed on the photoconductive medium 20 is transferred from between the photoconductive medium 20 and the first transfer roller 52 to the transfer belt 51.
The above developing and transferring processes are repeated with respect to the remaining three developing apparatuses 43, 44, 45. As a result, on the transfer belt 51 is formed a color image which is an overlap of the four colors. The color image is transferred from the transfer belt 51 to the paper P by the second transfer roller 53. The color image adhered onto the paper P in a powder state is fused on the paper P by the fusing unit 60.
However, the conventional image forming apparatus generates noise due to collision of the gap ring 48 of the developing unit 40 with the surface of the photoconductive medium 20 when the four developing apparatuses 42, 43, 44, 45 of the developing unit 40 approach the photoconductive medium 20 by the rotation of the turret 41. Additionally, due to the collision of the photoconductive medium 20 and the gap ring 48, the powdery toner image on the photoconductive medium 20 can be scattered and causes deterioration of the printing quality.